An electrical surface treatment device of the kind mentioned in the opening paragraph constructed as a vacuum cleaner and provided with an attachment of the kind mentioned in the second paragraph constructed as a suction attachment is known from EP-A-0 372 903. The surface type detector of the known vacuum cleaner is an acoustic surface type detector which is accommodated in the suction attachment of the vacuum cleaner. The vibration detector of the surface type detector forms part of an ultrasonic system by means of which a distance is measurable which is present during operation between the surface to be cleaned and a lower side of a suction nozzle of the suction attachment. If the ultrasonic system measures a comparatively great distance, the surface type detector delivers an output signal which is characteristic of a hard, smooth floor. If the surface to be cleaned is a carpet, an edge of the suction nozzle projecting beyond the lower side of the suction nozzle will sink partly into the carpet, so that the ultrasonic system will measure a comparatively small distance. In this case the surface type detector delivers an output signal which is characteristic of a carpet. The output signal of the surface type detector of the known vacuum cleaner is used for controlling an electric motor by means of which a brush arranged in the suction nozzle can be rotated and for controlling the sensitivity of an optical dust detector of the vacuum cleaner.
It is a disadvantage of the known electrical surface treatment device and the known attachment that the surface type detector used therein has only a limited distinguishing power, said surface type detector being capable of delivering substantially exclusively an output signal characteristic of a hard, smooth floor and an output signal characteristic of a carpet.